The proposal describes a set of five experiments designed to examine the cardiovascular effects on humans of social competition. Two populations of subjects differing in coronary-proneness (Type A's and Type B's) will be studied. Hypotheses derived from the Type A behavioral theory of coronary proneness will be tested. The major assumption of the theory is that Type A "situations" (competitiveness by others, time delays, etc.) stimulate the Type A "person" behaviorally (to be more competitive, aggressive, and controlling of others) and physiologically. Two-person competitive games, and computer-simulation of social competition, will be used to control social environmental events which are throught to be critical in triggering type A reactions. A laboratory computer will be used to monitor social behavior and physiological changes during the games. The laboratory model proposed offers a new level of control for studies of man-environment interactions in heart disease.